Aircraft are commonly equipped with one or more vision enhancing systems. Such vision enhancing systems are designed and configured to assist a pilot when flying in conditions that diminish the pilot's view from the cockpit, such as, but not limited to, darkness and weather phenomenon. One example of a vision enhancing system is known as a synthetic vision system (hereinafter, “SVS”) and may be more generally described as a being a dynamic condition subsystem of the aircraft. An example of a synthetic vision system is disclosed in U.S. Pat. No. 7,352,292 which is hereby incorporated herein by reference in its entirety. Additionally, an exemplary synthetic vision system is available for sale in the market place under product name SmartView, manufactured by Honeywell International, Inc.
A typical SVS is configured to work in conjunction with a position determining unit associated with the aircraft as well as with dynamic sensors that sense the aircraft's altitude, heading, and attitude. The SVS typically includes a database containing information relating to the topography along the aircraft's flight path. The SVS receives inputs from the position determining unit indicative of the aircraft's location and also receives inputs from the dynamic sensors on board the aircraft indicative of the aircraft's heading, altitude, and attitude. The SVS is configured to utilize the position, heading, altitude, and orientation information and the topographical information contained in its database, and generate a three-dimensional image that shows the topographical environment through which the aircraft is flying from the perspective of a person sitting in the cockpit of the aircraft. The three-dimensional image may be displayed to the pilot on any suitable display unit accessible to the pilot. Using an SVS, the pilot can look at the display screen to gain an understanding of the three-dimensional topographical environment through which the aircraft is flying and can also see what lies ahead. One advantage of the SVS is that its image is clean and is not obstructed by any weather phenomenon. One drawback of the SVS is its dependence upon the information contained in its database. If the database is not up to date, then the image presented to the pilot may not be an accurate depiction of the topographical environment around the aircraft.
Another example of a vision enhancing system is known as an enhanced vision system (hereinafter, “EVS”) and may be more generally described as being a sensor subsystem. Examples of enhanced vision systems are disclosed in U.S. Pat. Nos. 7,655,908 and 5,317,394 which are hereby incorporated herein by reference in their entirety. Additionally, an exemplary enhanced vision system is available for sale in the market place under product name EVS-II, manufactured by Kollsman, Inc. A typical EVS includes an imaging device, such as, but not limited to, a visible lowlight television camera, an infrared camera, or any other suitable light detection system capable of detecting light or electromagnetic radiation, either within or outside of the visible light spectrum. Such imaging devices are mounted to the aircraft and oriented to detect light transmissions originating from an area outside of the aircraft and are typically located ahead of the aircraft in the aircraft's flight path. The light received by the EVS is used by the EVS to form an image that is then displayed to the pilot on any suitable display in the cockpit of the aircraft. The sensor used in an EVS is more sensitive to light than is the human eye. Accordingly, using the EVS, a pilot can view elements of the topography that are not visible to the human eye. For this reason, an EVS is very helpful to a pilot when attempting to land an aircraft in inclement weather or at night. One advantage to an EVS system is that it depicts what is actually present versus depicting what is recorded in a database.
Some aircraft are equipped with both an EVS and an SVS. In such aircraft, the images from the EVS and the SVS are commonly shown to the pilot on the same display screen, with the image from the EVS being overlaid on top of the image from the SVS such that the portion of the SVS image located below the EVS image may not be visible.
In addition to the above described vision systems, additional images, in the form of symbology, are typically presented to the pilot on the same display screen where the images from the EVS and the SVS are displayed. The symbology commonly appears as an icon or a series of icons on the display screen and may be indicative of the aircraft's heading, direction, attitude, and orientation. Such symbology serves an important role in providing the pilot with situational awareness and controls concerning the orientation and attitude of the aircraft. This symbology is traditionally overlaid over the image presented by the SVS and the EVS.
The information provided by the EVS plays an important role in enabling the pilot to maintain situational awareness during the flight, and in particular, approach and landing during low visibility conditions. During certain portions of the flight, such as determining whether to proceed with a landing or to initiate a go-around procedure, the information provided by the EVS may have greater importance to the pilot than the information provided by the SVS.
At some point during approach (e.g., during a transition phase between a time prior to the point where an aircraft EVS system can perceive the runway until the pilot has a visual on the runway), the pilot may intuitively evaluate which of the EVS or the SVS is the more reliable or useable based on the current visibility conditions. When the EVS is determined to be reliable, the SVS system may be turned off. Although a display may include both an EVS image and an SVS image as a fused image (such as overlaying a semi-transparent EVS image onto an SVS image), or a side by side display, during this transition phase pilot heads up time and attention may be unnecessarily demanded.
Accordingly, it is desirable to provide systems and methods to automatically determine at what point in the approach phase the EVS can be objectively relied upon. In addition, it is desirable to reduce the work load on the pilot. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.